The registration of geodynamic signals in Geodynamic Laboratory in
Ksiaz (LG) started in 1974. Since that time strong signals were
irregularly occuring, which changed positions of equilibrium of the
pendulums. These effects reminded us the tilting of foundation, but on
account of constitution of quartz pendulums, it was difficult to
separate these signals from the instrumental drift (Chojnicki, Blum,
1996). Installation in 2003 in LG laboratory of two long water-tube
tiltmeters (WT) radically changed this situation. The new instruments
have sensitivity of three orders higher than the sensitivity of the
pendulums and the possibility of reducing the instrumental drift
(Kaczorowski, 2006). Shortly after beginning of measurements it turned
out that the irregular signals of strong variations of water level in
hydrodynamic system of WT correspond to tilting of foundation of 300
m.a.s. magnitude. All the effects except tectonic activity were
practically excluded as the source of these signals. Because the
structure of Ksiaz massif consists of non-absorbent rocks or, if they
are even partly saturated rocks--their level of saturation is very
stable in time, such strong hydrological effects are not possible.
Similarly loading effect of air pressure variations were excluded
because of magnitudes and time of duration of the phenomena. Also
activity of mines was excluded on account of too long distance between
Ksiaz laboratory and the mines (>50 km). The phenomenon of gravity
spilled of Ksiaz massif also does not explain the observed effects,
which show clear relaxation phase. Collected information on the
phenomenon, as well as increasing of length of data series confirmed
that irregularly occuring periodic non-tidal signals registered by WT
are of tectonic origin. The effects of tiltings and vertical motions of
foundation are observed during the tectonic events. Characteristic
course of the phenomena and their high repeatability can confirm
relationship between observed effects and tectonic motions in the
Sudeten Mountains region (Kaczorowski, 2009a). Observed by WT tectonic
deformations of sub-millimeter order, limits the possibility of
application of GPS/GNSS satellite technique for direct verification and
comparative works of tectonic phenomena. Nevertheless, this satellite
technique was applied for determination of KSIA station velocities,
expressed in the geocentric reference frame (ITRF2008) and for their
comparison with velocities of selected referential stations. These
stations, which were selected for further discussion, are distributed in
different distances and in different azimuths from KSIA station and are
situated on regional geological units. Until the end of 2013 KSIA
station registered over three years long data series on the basis of
which velocity vector was determined and applied by us in the first
attempt of interpretation. The yses of GPS data series provided us with
important geodynamic information in respect to the possibility of
stresses accumulation in unit of Swiebodzice Depression, as caused by
changes of relative distances between surrounding tectonic units and
Swiebodzice Tough (Teisseyre, 1951; Teisseyre et al., 1965). Generally,
accumulation of stresses in orogen manifests in form of tectonic
activity. In this issue we consider no seismic process of displacements
on faults in Ksiaz massif. After two years of low tectonic activity,
i.e. since 2009, there was initiated significant increasing of the
number of tectonic events and changes of proportions between magnitudes
of signals registered on both tiltmeters as well as in order of these
signals appearance. One of the main components of tectonic structure in
Ksiaz massif and in the surroundings of Geodynamic Laboratory is the
provisionally called by us and only for our local kinematic model
purposes 'main southern fault'. We expect that displacements
of wings of the 'main fault' may be ten times or more greater
than the displacements observed by WT on the indirect faults.
Displacements on the indirect faults are only transformation of
horizontal motion component and therefore ought to be much smaller. This
circumstance enhances chance, that the GPS stations, monitoring of the
'main southern fault', provides us with new information about
tectonic processes. Activity of the 'main southern fault' can
stimulate activity of indirect faults of the massif, which are
distributed under hydrodynamic system of WT. At present, the only
possibility of monitoring tectonic effects on the 'main fault'
is provided by application of GPS permanent stations, which are located
in relatively short distance (400m) and on the opposite wings of the
'main southern fault'. The new GPS station (KSI1) was
established on the building of castle stables in May 2013. We expect
that both GPS stations (KSIA and KSI1) will provide us with information
on the 'main fault' tectonic motions and will help us in
evaluation of the effect of regional stresses accumulation.

2. TECTONIC SIGNALS REGISTERED BY THE WATER-TUBES TILTMETERS

The water-tube tiltmeters are the main source of information
concerning tectonic activity in LG. In period of 2004-2007 the
water-tube tiltmeters registered five events of very strong signals with
maximum amplitude of 300 mas (ten times greater than the tidal signals).
The signals of water level changes had a very similar and characteristic
course of events which presents a very complicated picture (Kaczorowski,
2007).

The tectonic phenomena affect the water-tube tiltmeters through
tiltings and vertical motions of foundation. In data series of tectonic
signals it was possible to distinguish significant double-phase
character of tectonic phenomenon as well as simultaneous appearance of
tectonic signals on both tiltmeters, situated perpendicularly each
other. Until 2007 the signals observed on tiltmeter 01-02 contained
events of simultaneous decreasing of water level on both ends of the
tube of instrument. In several cases the tilting effects preceded the
effects of vertical motions of foundation. Together with increase of the
number of registered tectonic events and acquire of knowledge about
geological structure of Ksiaz massif, improvements were made in
kinematic models describing the tectonic phenomenon. Initial model with
simple tilting of foundation as well as model with vertical motions on
single fault, which crossed tubes of tiltmeters, did not allow to
explain the observed water level variations (Kaczorowski and Wojewoda,
2011). Until 2007 the five-elements model provided correct description
of water level variations during the tectonic event and it also
explained all characteristic moments of water level variations in
tiltmeters, caused by vertical motions and tiltings of foundation. In
the period of 2007-2009 there occurs an interval of low level of
tectonic activity, during which almost no tectonic signals were
observed. Since 2009 there follows significant increase of frequency of
tectonic events (Fig. 1 and Fig. 2). In March 2010 one extremely strong
effect amounting to 500 m.a.s., occurred on tiltmeter 01-02 (Fig. 1),
the previous signals on which were weaker than the signals on tiltmeter
03-04. In this time strong tectonic effects indicate small changes in
the course of events. On tiltmeter 01-02 there was a slight increase in
amplitude of registered signals, compared to the previous period, before
2007. However, after 2009 we still can observe events, the course of
which reminded the events from the previous epoch (Fig. 3).

3. INVENTORY OF RECOGNIZED FAULTS IN MASSIF OF KSIAZ LG

The collected observations from WT indicate that the tectonic
deformations of Ksiaz massif are proceed in three dimensions. Direct
horizontal component of tectonic motions is converted into tilting and
vertical motions of foundation. Vertical component of motions and
tilting of blocks in orogen are produced by effect of transformation of
horizontal component of motion on slope surfaces of faults. Therefore
the course of tectonic events takes form of horizontal and vertical
displacements of slope surfaces of faults, which depends on geological
constitution of Ksiaz massif. We recognized routes of the faults in
Ksiaz massif (in underground corridors of the LG as well as outside of
the underground, on the Earth surface), the part of which indicate
recent tectonic activity (Kaczorowski and Wojewoda, 2011). Geological
investigations confirmed existence of the system of parallel faults,
which cross the corridors with hydrostatic elements of WT. The collected
observations confirm that the tubes of tiltmeters, fixed to the
bedrocks, are affected by displacements of rocky blocks on active
faults.

In spring of 2013 measurements of recognized faults were made as
well as calculations of their routes and dips. For these calculations
three dimensional geodetic network was established in autumn of 2012,
inside the underground corridors of the LG. The local network was
connected with external points of geodetic network, using precise
tachymeter and GPS equipment. The accuracy of the network is less than 1
cm in both the horizontal and vertical components. All of the determined
faults can be divided into two separate classes of similarity on the
basis of their routes and dips (Fig. 4). It was proved that in the Ksiaz
massif there are two dominant systems of faults belonging to two
separated classes. The faults of the first class are parallel to the
'main southern fault' (Class 1 in Fig. 4) whereas the azimuths
of routes of the second class faults (Class 2 in Fig. 4) differ by
~30[degrees] from the west (counterclockwise) in relation to the azimuth
of the 'main southern fault'. The third class of faults (Class
3) consists of only two but large and clearly marked faults,
continuation of which is clearly visible outside the corridors of the
laboratory, on exposed rock slopes. The azimuth of faults of Class 3 is
almost perpendicular to the azimuth of the 'main southern
fault'. The first two classes of the faults occur in tectonic
deformations of orogen in different manner. Probably the faults of Class
1, which are parallel to the 'main southern fault', are active
in situation when northern wing of the 'main southern fault'
is slower than its southern wing. In inverse situation, when the
northern wing is faster than the southern one, Class 2 of the faults is
active. Taking into account geological indicators of delay of the
northern wing in relation to the southern wing, we named the first case
as 'compensation phase' of phenomenon and the second case as
'shifted phase'. This thesis is motivated by changes of faults
activity observed after 2009 by wT tiltmeters (see Chapter 2.).

We construct the three dimensional kinematic model of Ksiaz castle
hill massif with strike of faults in order to better recognize this
situation. The kinematic model will provide us with better determination
of influence of tectonic activity on water-tube tiltmeters. At the
present stage of our research on the phenomena and effects recorded by
the measuring equipment installed in LG Ksiaz, an attempt was made to
build the simplest kinematic model describing the behavior of the
fragments of the massif (block) of rock, in which are hollowed the
underground corridors of our laboratory and which at the same time would
be able to describe and explain the complexity of these strong signals.
This model, of course, must be at the most consistent with the real
conditions that exist in this physical space. Massif, on which the Ksiaz
castle is built is surrounded on three sides by the valley of Pelcznica
river. To a depth of approx. 100 meters (LG lab is sitted at a depth of
approx. 50 m under the buildings of the castle) we can treat it as
partially relaxed rock mass and attempt to model the mutual
displacements of individual fragments of rock, carried out on existing
cracks surfaces and faults. In this part the massif would not be subject
to any rheological processes directly, that does not mean that they may
not occur in the deeper layers, located under the level of the Pelcznica
river bed. From the study of the terrain topography we can expect that
the only direction of the origin of source of stress in the upper layer
of rock-mass is North or North-East. From the same analysis of
topography, we noted a strong deformation of the meander of the
Pelcznica river, which, from the South-East in relation to the Ksiaz
castle, instead of bending the line of close to cycloid shape, it bends
almost at right angles. Such a meander shape indicates the possibility
of the occurrence of the fault location, on which would occur this type
of deformation. In the literature, there are geological notes and maps,
on which are inscribed the faults routes which can confirm this thesis.
If that is the case, then the generated stress in the upper layers of
the crust could be compensated (discharged) through the interaction of
the two wings of the fault. In view of our current research
capabilities, first we try to detect possible activity of the 'main
southern fault', with potentially the greatest deformations,
especially in horizontal component, and due to the fact that we have two
GPS receivers installed on both wings of the so-called 'main
southern fault'. We have also made the effort to place the precise
measuring equipment inside the LG, which possibly indicates the
existence of much smaller movements on the indirect faults, which are
recognized and measured inside the underground corridors of the
laboratory.

4. GPS STATIONS IN LG (KSIA AND KSI1)

Detailed description of conditions of selection of the site for
installation and mounting of GPS antenna system, installation of station
infrastructure as well as description of registration data parameters
and adopted methods of GPS data processing are included in the previous
publication (Zdunek, 2012). Since autumn of 2010 GPS station KSIA has
equipped with TurboRogue SNR-8000 receiver and Trimble D_M ChokeRing
(TRM29659.00 NONE) antenna. Small number of channels in the Turbo-Rogue
receiver caused limitation of the number of registered observations, so
on 2012-10-13 (2012:DOY287) it was exchanged for Ashtech uZ-CGRS. What
is very important for construction and ysis of time series of station
coordinates, the stabilization of the antenna, the antenna and signal
cable were not changed. As a result of the exchange of the receiver
there occurred a slight improvement in the accuracy of station
coordinates obtained from daily solutions. Average error values
decreased by 15 %, 24 % and 13 %, respectively for B, L and h component.
Since the commencement of permanent registration, i.e. from date of
2010-11-13 (2010:DOY317) to 2013-11-17 (2013:DOY320), for 1100
observation days 1097 whole day sessions were registered. Collected over
3-year series of continuous observations is still elongated and
developed to systematically improve the accuracy of determination of
KSIA station velocity vector. In order to support the research of mutual
horizontal displacements of wings of the main southern fault, in autumn
of 2012, exploration of the possibilities of establishing a second GPS
station, positioned at the southern side of the fault was performed.
Finally it was established on the building of castle stables, in May
2013 (Fig. 5).

On the new GPS station KSI1 operates, removed from the KSIA
station, Turbo-Rogue SNR-8000 receiver and Rogue Dorne-Margolin Choke
Ring (AOAD/M_T) antenna without snow cover. ysis of the data from the
second GPS station show that the quality of observations is at the same
level as for the KSIA station during the period when it worked with the
Turbo Rogue receiver.

5. GPS DATA ANALYSIS AND RESULTS

GPS data processing are performed using two different methods:
'Precise Point Positioning' (PPP) (Zumberge et al., 1997;
Kouba et al., 2001; Bisnath et al., 2008), as well as 'Double
Differences' (DD). PPP solutions, though somewhat less precise,
allow us to avoid of possible influence of GPS reference network
construction changes, that quite often occur at long time intervals of
data processing. The first method of data elaboration is realized by
means of Canadian program NRCan-PPP, the source code of which was
rendered to us basing on a signed agreement. For the second method (DD),
initially the Bernese GPS Software ver.5.0 was used (Dach et al., 2007).
After the release of version 5.2 of the program, in July 2013, due to
significant changes, including implemented new geophysical models and
parameters, recommended by the IERS conventions (Petit and Luzman,
2010), the decision was made to perform a re-processing of the whole
observational material. Its completion is planned for the first quarter
of 2014. Similarly, it was also in the case of PPP processing. The whole
material was re-processed in the last version of the program: 1.05/03812
on 2013-01-07. This process has been completed. Based on the results
from GPS data, time series of station coordinates are constructed for
the KSIA station and for the stations close and further its
surroundings, established on the other geological structures. Presented
in this publication results, obtained from GPS technique, end at the
epoch of 2013-11-16 (2013:DOY320). For the most stations it cover nearly
6 years of observation. Data from CLIB and CPAR stations are available
from the date 2009-12-17 (2009: DOY351), which gives nearly 4-year
series. The shortest period of GPS observations has the KSIA station,
which collected data from 3 years. The length of this period is taken as
the minimum for the purposes of station velocity vectors calculations,
determined from GPS technology. In the period covered by the GPS data
processing, several events occurred that had an impact on the quality
and consistency of the constructed time series of stations coordinates.
The reference frame, in which all GPS data processing variants are
realized, is the current reference frame of precise orbits of GPS
satellites and global parameters consistent with them. On 2011-04-17 the
new reference frame ITRF2008 (IGS08) was implemented into IGS products,
which, in GPS component, first time is based on absolute GPS/GNSS
antennas models. In addition, on several selected EUPOS/EPN stations,
changes in GPS equipment (receiver/antenna) took place during the period
of the elaboration data: BISK: 2012-11-11 (receiver), CLIB: 2010-05-18
(receiver), 2011-09-01 (receiver+antenna), CPAR: 2011-10-27 (antenna),
2011-11-10 (receiver), GOPE: 2009-12-15 (receiver+antenna), WROC:
2012-10-22 (receiver +antenna). On 2012-02-14 (2012: DOY045) IGS/EPN
station BRUS was definitively closed, forcing us to its replacement
during the re-processing. In addition, in 2011 and 2012 a lot of longer
intervals with missing GPS observations took place on the stations METS,
JOZE, BISK and some other stations. All reference stations of IGS/EPN
networks included in the data processing belong to the class A of these
networks, which is consistent with the recommendations for IGS/EPN
networks densification (Gurtner, 1994; Bruyninx et al., 2013).
Construction of the station coordinate time series, which started in the
ITRF2005, after changing the reference frame is done in the new
ITRF2008. All designated solutions to the epoch 2011:DOY106, which were
referred to the ITRF2005 (IGS05), have been converted to the new
reference frame ITRF2008, using the 14-parameter transformation,
officially recommended by the IERS (Altamimi et al., 2012).

(http://itrf.ensg.ign.fr/ITRF_solutions/2008/tp_08-05.php). Due to
the different lengths of the time series for different groups of
stations, it was decided at this stage, to determine simultaneously the
coefficients of the linear expressions (to calculate the trend of annual
changes in horizontal components of stations coordinates) as well as
only one periodic expression annual seasonal effects, which is an
obvious element of physical effects on the periodicity of change.

Table 1. contains a list of the values of the velocity vectors (its
horizontal components) as well as the amplitudes and phases of KSIA
station and selected ASG-EUPOS/CZEPOS/EPN stations, involving
(different) time intervals available for each station, and determined
from the PPP solutions.

As it shown by existing yses carried out on various lengths of time
series, for shorter time intervals we generally obtain values of the
station velocity vectors slightly overestimated in relation to
determinations involving longer intervals. Table 2 provides examples of
the determinations for the periods of the last 3 and 6 years. An
exception are CLIB and CPAR stations, for which observation data are
available from the last less than 4 years.

This effect also occurs at the station KSIA. Processing of longer
intervals of GPS data will enhance credibility determinations of the
station velocity vectors and should eliminate this effect.

In order to make initial external evaluation of the obtained values
of stations velocity vectors, 3 IGS/EPN reference stations, located
closest to the KSIA station, were compared with values, published in the
official catalog of ITRF2008 and with velocities calculated from SOPAC
as well as JPL time series. Determined velocity vectors show a high
compatibility with each other, especially in the length of the vectors.
Computed velocities are closest to the values in ITRF2008 catalogue.
Greater differences can be caused e.g. by the fact, that they were
determined based on a significantly different intervals of observations
(Table 3).

Another comparison was made with vectors calculated using existing
models of tectonic plate movements, obtained from geophysical and
satellite techniques. These models, due to the slightly different
assumptions (De Mets et al., 1990; Drewes, 2009; Argus et al., 2010),
show differences of absolute values, but between adjacent stations get
very high consistency, well describing the generalized movement of the
EURA continental tectonic plate. From last two columns we can see more
complicated pattern. They show that, especially vectors for stations
located in the Sudeten Mountains are differ more from the values
calculated from models. These stations can be affected by intra-plate
tectonic movements (Table 4, Fig. 7).

6. PRELIMINARY INTERPRETATION

Now we know that observed by WT effects, associated with recent
tectonic movements in the Ksiaz massif are event-driven, rather than
continuously. Due to the interaction of adjacent geological structures
(massifs, blocks) event-driven nature of these movements relates
probably to much larger area of the Sudeten Mountains than Ksiaz massif.

Conducted in Ksiaz LG since autumn 2010 GPS measurements are
intended to help answer the question whether the behavior of the Ksiaz
massif stands out from its surroundings or the motions of the KSIA
station are subject to the same trends as the rock mass movements of
station Ksiaz. The answer to this question will conclude whether the
observed LG manifestations of contemporary tectonic activity are the
result of cumulative stress on a larger scale (in the region) or only
locally in the rocks of Ksiaz massif. The assumption, the determined
velocity vectors are the vectors representing the physical displacements
of the stations on the Earth surface, allow us the evaluation of the
potential impact of stress caused by adjacent geological structures on
the rock mass Ksiaz. With this subject they are included at this stage
to develop a preliminary interpretation of the phenomena observed by
water-tube tiltmeters in LG. On the basis of determined the absolute
velocity vectors of the stations in the ITRF2008 reference frame, for
the ysis and interpretation purposes, differences of velocity vectors of
each selected station and KSIA station was calculated, whereas the GPS
KSIA station has the greatest uncertainty (Table 5, Fig. 7).

Based on the determined stations velocity vectors and comparisons
with existing tectonic plate movement models, it can be seen that in
addition to the dominant effect, which is the vector of mean movement of
continental plate EURA in this region, in the study area have also
occurred intra-plate movements with values of approximately 1 mm/year or
less. In particular, this effect is visible on the stations located in
the Sudeten Mountains and the Sudeten Foreland. Determined horizontal
components of stations velocity vectors, due to the existence of the
strongly dominant effect of EURA tectonic plate motion expressed in the
ITRF2008 reference frame, have similar azimuths. An average value in
this region is about 53.4[degrees] with small fluctuations on a few
reference stations (less than 1[degrees]). Only a few stations, mostly
lying on the south side of the Sudeten Mountains and in their area
slightly exceeded this value. Estimated azimuth of station velocity
vector of KSIA station is about 53.8[degrees] and forms with the azimuth
of the main southern fault (approx. 44.9[degrees]) small angle of about
8.9[degrees] (Fig. 5).

Close-up the angular of direction of the main southern fault and of
the determined velocity vector of KSIA station causes that the movement
of the wings fault acts on the speed of movement of the station and not
on a change of the azimuth of the movement. From the distribution of the
relative vectors can be concluded that the rock mass Ksiaz moves a
little faster in the north-east direction than the area of the Middle
Odra region and stations in the Czech Republic (in the south of Sudeten
Mountains). Comparison of horizontal velocity vectors for stations lying
in the direction of the 'main southern fault' follows, that
today it is possible occurrence of stress of the Earth's crust on a
regional scale. During the period of last few years the stress component
can be similar to the azimuth of the 'main southern fault'.
This thesis, however, requires longer studies. From results of the half
a year of the data series of 400 m long GPS vector KSIA-KSI1, we can see
appearing trend of shortening its distance. This results (~1.2 mm/year)
is still of a low level of credibility. However, this could indicate the
presence of a faster move of the north wing in a north-east direction in
relation to the south wing of the main fault, which is evident in the
geological and morphological indicators, shown in Figure 5. The velocity
vector of the neighboring stations WLBR and other stations located in
the Sudeten Mountains suggests the possibility of interaction of
adjacent geological structures on Ksiaz massif.

7. CONCLUSION

The 'main southern fault', which is the central element
of our local kinematic model for Ksiaz massif, runs in about one hundred
meters distance from GPS station KSIA, established in Ksiaz LG. It is
probable that increase of velocity vector of GPS KSIA station in
relation to the velocity vector of the GPS reference stations is created
by influence of movement of the 'main southern fault' wing
(Fig. 4., Fig. 5.). The local vector of displacements of the northern
wing of the 'main fault' interfere with the mean vector of
large scale continental plate motions in this region. Determination of
differences of velocity vectors of GPS KSIA station and mean velocity
vector of GPS reference stations allowed us to evaluate velocity of the
northern wing of the 'main southern fault'. Determination of
azimuth and trend of displacements occurred on the 'main southern
fault' simplify interpretation of medium deformations on indirect,
secondary faults, which exhibit vertical motions and tilting of
foundation. Recognized and measured faults in underground corridors of
LG laboratory, crossing WT tubes, show that the proposed multi-fault,
five-elements model, which describes the observed tectonic events is
consistent with the existing state of the faults, especially with the
Class 2 of indirect faults. In respect of dominant meaning of the
'main southern fault' we decided to mount the second GPS
station (KSI1) on the southern wing of the 'main fault' in May
2013. We expect that GPS station KSI1 provide us with data about mutual
displacements of wings of fault as well as information about
displacement of the southern wing of the fault. On the basis of the half
a year data series of KSI1 station we conclude that the distance
connecting both stations (cca 400 m) shortens. This result is still of a
low level of credibility. Besides the GPS stations located on the
'main southern fault', there are no other measurement
instruments such as feeler and extensometers gauges, which are more
suitable for monitoring displacements on faults than the satellite
measurement techniques. Installation of these instruments is planned and
it will allow us for a more precise recognition of faults mechanism.
Complete the re-processing of GPS data in the Bernese Software V.5.2 and
the successive lengthening of the time series being developed by both
methods also will allow in the future for their verification and
improvement of the developed model of the phenomenon.

DOI: 10.13168/AGG.2014.0016

Article info

Article history:

Received 24 February 2014

Accepted 6 September 2014

Available online 6 October

ACKNOWLEDGMENTS

The GPS stations in Ksiaz Geodynamic Laboratory and related
research was financed by the grant No. N N526-159538 of the Polish
Ministry of Scientific Research and Information Technology. The
water-tube tiltmeters was founded by grants 4-T12E011-28, N N526- 160536
and earlier.

Altamimi, Z., Collilieux, X., Legrand, J., Garayt, B. and Boucher,
C.: 2007, ITRF2005: A new release of the International Terrestrial
Reference Frame based on time series of station positions and Earth
Orientation Parameters. J. Geophys. Res., 112, B09401. DOI:
10.1029/2007JB004949

Kaczorowski, M.: 2008, Non-tidal plumb line variations observed
with help of the long water-tube and horizontal pendulums tiltmeters in
Geodynamic Laboratory of PAS in Ksiaz. Reports on Geodesy, 85, 2, 79-86.